The Star -Fish. 27 



Oar new friend is called a star-fish, from its shape like 

 a star with five points, which we call rays or arms. Its 

 home is in the sea, on the piles of wharves, among the 

 rocks, or on oyster and mussel heds. In summer it is 

 often found above low-water mark in tide pools, but in 

 winter it takes refuge in deeper water. When dried it 

 gives us no idea of the rich colors, — red, bluish, green, or 

 brown, — with which it beautifies the sea-bottom. Unlike 

 most of the animals so far studied, it can move slowly 

 from place to place. 



The children at once find the mouth, but we wish to 

 study the back first, " the side that is rough all over." 

 (Fig. 1.) Holding this uppermost we find the sieve, a 

 round, coral-like spot that is red or orange when the star- 

 fish is alive, and used to filter the water that passes in 

 through it. The central part of the star-fish is the disk. 

 The sieve is on one side of the disk, near the angle where 

 two rays meet. If now a line is drawn from the sieve 

 across the disk and through the middle of the opposite 

 ray, there will be the same number of rays 

 on each side of the line, that is, the star- 

 fish will be divided in halves. 



This gives ns a hint of the bilateral sjmmetry 

 seen more perfectly in the higher forms. 



The back of the star-fish is covered 

 with knobs, — " prickers," the children may 

 say, — called spines. They are short and 

 Fig. 2. rounded at the tip, and we find by trying 

 them on alcoholic specimens, that they do not move. 

 Between and around the spines are little things looking 

 like tiny grains of meal, which are two-pronged forks, or 

 pedicellarise (Fig. 2), always opening and shutting. We 

 do not know their use, unless it is to keep dirt from cling- 

 ing to the star-fish. On alcoholic specimens these will 



